1. Field of the Invention
The present invention relates to a carburetor of the type, in which the air injected from an air nozzle is made to impinge upon the fuel spurting from a main nozzle so that the flow rate of the fuel from the main nozzle may be suppressed and controlled by the impinging force of the air from the air nozzle.
2. Description of the Prior Art
As the carburetor of the above type, we have already invented both a carburetor C.sub.1, as is schematically shown in FIG. 1, and a carburetor C.sub.2 which is slightly improved over the carburetor C.sub.1 and has its improvement shown schematically in FIGS. 2A and 2B.
In these carburetors C.sub.1, as shown in FIG. 1, the control air passage 18 has its inlet port 18a connected with an air filter A at a downstream position of the filter element thereof and its outlet port 18b within an intake passage. Between the inlet and outlet port 18a, 18b, there is disposed either a control valve 19, which is opened and closed by a control circuit 25 in response to the output of an oxygen sensor 24 made operative to detect the oxygen concentration in the exhaust gases of an engine E, or a flow regulating valve, which has its opening continuously or stepwise increased or decreased. An air nozzle 20 at the exit of the control air passage 18 is opened to protruded into a small venturi 3 of an intake pipe (intake passage) 1. The air nozzle 10 is provided to oppose to a main nozzle 10 at the exit of a main fuel passage 8 and the main fuel nozzle 10 is also opened to protrude into the small venturi, so that the two nozzles 10 and 20 are arranged at a position, where the air sucked from the air nozzle 20 is made to impinge upon the fuel sucked from the main nozzle 10. The impinging force of the air, which is injected from the air nozzle 20 for changing the flow rate of the fuel sucked from the main nozzle 10, is subjected to either an ON-OFF control by the control valve 19 as a throttle means or an analog or digital control by the flow regulating valve 19 thereby to control the air-fuel ratio of an intake mixture.
In the carburetor C.sub.2 as shown in FIGS. 2A and 2B, on the other hand, either a dis-bar (distribution bar) 26 having such a semicircular cross-section as is fitted on the outer circumferences of the two nozzles 10 and 20, as shown in FIGS. 2A and 2B, or a dis-bar having another cross-section is disposed to extend at the inlet side of the small venturi 3 across the main nozzle 10 and the air nozzle 20, which protrude into the small venturi 3 in a manner to face each other, so that the air flow, which is injected from the air nozzle 20 to impinge upon the sucked fuel from the main nozzle 10, is prevented from being sharply deflected by the intake air flow passing through the small venturi 3 thereby to weaken the impinging force of the air injected from the air nozzle 80.
Although, in the carburetors C.sub.1 and C.sub.2 shown in FIGS. 1 and 2A and 2B, the air passage 18 has its air inlet disposed downstream of the air filter A, the present invention should not be limited to such construction but can be applied to the carburetor C.sub.1 ', as shown in FIG. 3, in which the air passage 18 has its air inlet opened into a separate compressed air source (CAS) while allowing others to have the same construction as the aforementioned one.
With this in mind, we have conducted systematic experiments and analyses with a view to enhancing the performance of the carburetor under consideration. These experiments and analyses have revealed that, in the carburetors C.sub.1, C.sub.1 ' and C.sub.2, the impinging force of the air flow injected from the air nozzle 20 can be adjusted to a desired strength by selecting the relative sizes, positions and angular relationship between the two nozzles 10 and 20 at a predetermined proper value and combining them. In the case of the most proper selection and combination thereof, the impinging force can be strengthen so the the range, within which the flow rate of the fuel to be sucked from the main nozzle 10 can be changed by that impinging force, and accordingly the range, within which the air-fuel ratio of the intake mixture can be controlled, can be widened.
With the use of such carburetors, moreover, the Inventors have conducted several series of experiments and analyses, while suitably selecting and combining the relative sizes, positions and angular relationship of the air nozzle and the main fuel nozzle, to find out the most proper sizes, positions and angular relationship that can make the impinging force of the air flow from the air nozzle the most proper thereby to widen the range, within which the flow rate of the fuel to be sucked from the main nozzle can be changed by that impinging force, and accordingly the range, within which the air-fuel ratio of the intake mixture can be controlled.